Prior-art screw presses are known to comprise two slides, i.e., inner and outer ones. The outer slide serves for locking and clamping the die, while the outer slide deforms the blank in a closed die. Such presses serve for producing the forgings of a definite type, e.g., hubbed gears, flanges, and the like, which are produced by single-ended pressing of the blank.
To produce a definite kind of forgings, such as, say, stem-pinion, closed-die forging by virtue of double-ended pressing should be resorted to.
Deformation by virtue of double-ended pressing is preferable to single-ended as the source of plastic deformation is arranged symmetrically, there occurs no restriction to plastic of a single-ended deformation, losses due to friction of metal against the die walls are reduced and specific efforts applied are diminished.
Another hydraulic screw press operating on the double-ended pressing principle is known to comprises a horizontal frame which mounts the slides carrying female die halves and the slides carrying male dies, both of said groups of slides being adapted to reciprocate against each other, each of the slides having a self-contained drive of its own. The male-die carrying slides obtain drive from hydraulic cylinders linked with their movable members to said slides through lead screws which are adapted to interact through their threading, with the flywheels rotatably mounted on the frame. The lead screws are locked-in with the slides, whereas the interior space of the hydraulic cylinder is in fact the hollow of the lead screw and the cylinder rod is made fast on the frame.
The slides carrying the female die halves is imparted motion from hydraulic cylinders which are also adapted to establish the clamping force for the die halves in the course of the press-forging process.
To establish synchronism of movement of the slides carrying the male dies, the slides are interconnected through the lead screws provided with a non-selflocking thread (cf. USSR Inventor's Certificate No. 294,411).
In the press discussed hereinbefore, torque reaction resulting from interaction of lead screws and flywheels, is relayed to the slides since they are locked-in with the lead screws, and further on to the frame ways. This leads to an abnormally high wear on the ways, disturbs their adjestment and affects adversely the travelling accuracy of the slides which in turn tells badly on the dimensional accuracy of forgings produced, reduces the endurance of the die sets and reliability and service life of the press as a whole.
The dimensional accuracy of forgings is also affected by the presence of considerable axial plays in the non-selflocking thread of the lead screws in the travelling synchronization system of the male-die carrying slides.